Falling long-term bond yields are pressuring banks, but there is a potential bright spot: Lower rates are spurring people to refinance mortgages and buy new homes.

Wells Fargo & Co., the nation’s largest mortgage lender by origination volume, said Thursday that it expects mortgage volume industrywide to be 20% to 25% higher for the year than the roughly $1.5 trillion it initially anticipated. J.P. Morgan Chase & Co., the second-largest mortgage lender, also said Thursday that industry volume could be up by 50% this...